112 NATURAL HISTORY. 



The reason why the same animals are to be found in the northern 

 parts is the nearness of the two continents. They are so near as to be 

 within the power of accident to bring the animals, especially the large 

 ones, from one continent to the other ; either on the ice or even by 

 water. But the continents diverging from each other, southward, so 

 as to be at a very considerable distance from each other, even beyond 

 the flight of birds, is the reason why the quadrupeds [of those southern 

 regions] are not the same [in both continents]. 



It is reasonable to suppose that those animals were natives of either 

 continent, and of the northern parts, and that those animals which are 

 spread over all the old continent, but domesticated, such as horses, 

 asses, cows, sheep, some deer, hogs, &c, were animals of the more 

 southern parts, and that their universality in the colder parts is only of 

 modern date. 



Most animals, probably, have the disposition to keep to their place 

 either of nativity or adoption. Those that are not animals of passage, 

 of course keep to their place of nativity ; but this is much more con- 

 fined in some than in others. A pigeon [the Rock-pigeon, Golumba 

 livia, e. g.] keeps to the very spot, viz. house or rock, even to the 

 same hole ; a dove [the King-dove, Columba Palumbus, e. g.] keeps to 

 the wood, but not to the same spot or tree ; therefore, it wanders a 

 little. But birds of passage, I believe, only keep to their place of 

 adoption, and this very strictly. A swallow builds, if allowed, in the 

 same nest or same corner of a window. Thus animals which have taken 

 up a residence, whether their native one as in the case of the pigeon, or 

 their adopted one as in that of the swallow, crow, magpie, &c, keep to 

 the same place. The circumstance of adopting a place, shows that the 

 young of these do not keep to the same rules, only those which keep to 

 their place of nativity. 



Some animals burrow for protection, habitation, &c, as the badger; 

 others for their livelihood, as the mole, and probably the mole-cricket. 



